Recently, the market of rechargeable battery is rapidly expanding. Particularly, non-aqueous rechargeable battery, for example, lithium ion rechargeable battery is widely employed as battery for portable electronic equipment such as a small-sized portable computer and portable telephone unit.
Lithium ion rechargeable battery used as a battery pack in the form of a single battery or a set of batteries is deteriorated in safety and quality due to over-charge and over-discharge. Accordingly, in order to maintain the safety and reliability, a control circuit for preventing over-charge and over-discharge is generally mounted on BMU (Battery Management Unit) in the battery pack for the purpose of management of battery voltage, etc.
In equipment with lithium ion rechargeable battery mounted, full-charge detection is often executed in the battery pack. In this case, CC (Constant Current)/CV (Constant Voltage) control is executed by a charger, and drooping of the current is checked by BMU, and full-charge detection is executed when the current reaches a value less than the value set at a certain temperature. In that case, in order to prevent faulty detection, it is an additional condition that the measured value of total battery voltage is higher than a certain value.
On the other hand, for further improvement of safety, recently proposed is, for example, a function of self-checking by BMU as is disclosed in Japanese Laid-Open Patent No. 1-234910.
FIG. 7 shows a flow chart of charging control including trouble checking.
As shown in FIG. 7, when over-current, over-charge or over-temperature trouble is detected (steps S1, S2, S3), a charging FET (Field Effect Transistor) that is a semiconductor element for closing the charge-and-discharge circuit of BMU added to the battery pack is turned OFF (step S7) to perform the checking of the charging FET (step 8). As a function of detecting the trouble of the charging FET, often employed is a method of cutting off the fuse disposed in the charge-and-discharge circuit after detecting that the charging current keeps flowing even with the charging FET forcibly turned OFF (step S9).
However, in the method described above, there arises a problem such that the charging operation is not suspended but continued even in case the measured value of battery voltage becomes too low, the total battery voltage is not increased, or full-charge or over-charge is not detected at all.
The present invention is intended to solve the problem, and its object is to provide a BMU which is, in addition to conventional over-charge protection, capable of integrating the charge to check for charging capacity trouble, self-checking the trouble of battery pack and discontinuing the charging operation, keeping the battery pack or electronic equipment and systems having the battery pack in safe condition, and storing trouble information to prevent execution of re-charging during generation of trouble.